Grinding machine

ABSTRACT

In a grinding machine comprising a stationary wall part and a plate part which rotates about an axis of rotation, between which a gap is formed, the gap is limited from above by a ceramic part and from below by an elastic part.

[0001] This application claims Paris Convention priority of DE 200 18805.4 filed Nov. 3, 2000 the complete disclosure of which is herebyincorporated by reference.

BACKGROUND OF THE INVENTION

[0002] The invention concerns a grinding machine having a stationarywall part and a plate part, which can rotate about an axis of rotation,wherein a gap is formed between the stationary wall part and the platepart.

[0003] A grinding machine of this type is disclosed in DE 196 06 117 A1.Such a grinding machine operates under the influence of centrifugalforce. Workpieces to be treated and grinding material are disposedwithin the inner space formed by the wall and the plate part, androtated through rotation of the plate part to effect a polishing effectthrough the influence of centrifugal forces and the relative speedsbetween the workpieces and grains of grinding material.

[0004] In a known embodiment, the annular gap between the rotary platepart and the stationary wall part is limited from the upper side by anelastic lining of the wall part, and, on the lower side, by a ceramicring disposed on the rotary plate. The ceramic ring has a rectangularcross-section. The plate part is formed directly below the ceramic ringand tapers inwardly towards the bottom. While the elastic lining, due toits elasticity, is hardly worn by the grinding material bodies, it hasturned out that the ceramic ring experiences large wear as a result ofcontinuous exposure to grinding bodies, wherein, in particular, grindingmaterial bodies collect in the gap and, through their abrasive effect,grind down the ceramic ring in the region of its inner upper edgethereby forming a step having a depth of 3 mm to 5 mm, within a shortperiod of time. Grinding material can collect therein and accumulates upto the lower edge of the lining of the stationary wall to cause furtherwear of the ceramic part in response to the relative motion between thewall and the plate parts. The ceramic part must therefore be replacedafter a short period of time.

[0005] It is the underlying purpose of the present invention to furtherdevelop a grinding machine of the above-mentioned type which has alonger service life.

SUMMARY OF THE INVENTION

[0006] This object is achieved in accordance with the invention by agrinding machine of the above-mentioned type, characterized in that thegap is limited from the top by a ceramic part and from the bottom by anelastic part. It has surprisingly turned out that, compared to priorart, the abrasive effect of the grinding material bodies on the ceramicpart is much less if the ceramic part is disposed on the lower side ofthe stationary wall, wherein the ceramic ring limits the gap from above.The gap is limited from below by the elastic lining of the rotary platepart. The reason for the reduced wear may be that, although a small stepalso forms in the region of the inner lower edge of the ceramic ring dueto the abrasive effect of the grinding material bodies, grindingmaterial cannot collect and accumulate therein, since it is constantlyremoved by the undamaged opposite edge of the elastic lining of theplate part.

[0007] The invention therefore provides for a much longer service lifecompared to prior art. The ceramic ring must only be replaced after amuch longer period of use.

[0008] The elastic part of the plate part is preferably a lining thereofwhile the ceramic part is a ceramic ring. Preferably, surfaces areprovided between the two opposite planes which are preferably orientedhorizontally and perpendicularly with respect to the axis of rotation.They can also incline slightly towards the inside with respect to thehorizontal, e.g. in a range of 10° to 30°. The axis of the grindingmachine is usually vertical. A particularly preferred embodiment of theinvention is characterized in that the ceramic part has a nose-likeprojection extending downwardly, wherein, in particular, the inner wallof the plate part and wall part are formed substantially conically,tapering from the top towards the bottom above and below the gap. Theconical inclination of the inner wall with respect to the vertical axisof rotation can thereby be 30° to 45°. Both, this inclination of theplate part directly below the gap as well as the conical inclinationextending inwardly and downwardly of the inner wall of the wall part,support the abrasion-preventing arrangement of the gap-limiting ceramicpart on the upper wall part and the elastic part of the rotary platelimiting the lower side of the gap.

[0009] Further advantages and features of the invention can be extractedfrom the claims and the following description which show, in detail, anembodiment of the invention with reference to the drawing.

BRIEF DESCRIPTION OF THE DRAWING

[0010]FIG. 1 shows a vertical section through a preferred embodiment ofthe inventive grinding machine, partly cut; and

[0011]FIG. 2 shows an enlarged detailed representation of the device ofFIG. 1.

DESCRIPTION OF THE PREFERRED EMBODIMENT

[0012]FIG. 1 shows a vertical longitudinal section of a preferredembodiment of an inventive grinding machine 1. The grinding machine issymmetrical about its axis of rotation A such that substantially onlythe right part of the vertical section is shown. The inventive grindingmachine 1 comprises a stationary wall part 2 below which a plate part 4is provided which is rotated about the axis A by a drive shaft 3.Outside of the plate part 4 and surrounding same a stationary lower part6 can be adjacent to the lover side of the wall part 2. These componentsare substantially metallic, e.g. aluminum. The wall part 3 and thebottom part 4 have an elastic lining 7, 8 on their inner side,preferably of polyurethane. The lower side of the wall part 2 comprisesa ceramic ring 9 which is firmly connected to the wall part 2.

[0013] The lower region of the inner wall of the elastic lining 7 andthereby of the wall part 2 exhibits a tapered inclination with respectto the vertical line defined by the axis of rotation A, wherein theangle of inclination can be in the range of e.g. 30° to 45°. The ceramicring 9 has an inner wall 11 which substantially extends at that sameinclination and an upper wall side 12 and rear wall 13 which aredirected substantially perpendicular to each other and perpendicular andparallel with respect to the axis A, respectively. The lower inner sideof the ceramic ring has a nose-like downwardly extending projection 14which merges in its rear region, via an inclination 16 slanting upwardlyfrom an edge 16 a and outwardly, into an outer lower wall region 17extending horizontally, perpendicular with respect to the axis ofrotation A, up to the outer edge 17 a of the ceramic ring 9. Theinclination 16 can also extend continuously from the edge 16 a to theedge 17 a, wherein the horizontal region 17 is omitted.

[0014] The upper side 19 of the elastic lining 8 of the plate part 4angles outwardly to form a projection 18, which extends substantiallyalong the upper side 19 of the plate part 4. The upper surface of theprojection 18 is flat and extends parallel to the lower side of the nose14 a.

[0015] The grinding machine 1 is operated by inserting workpieces, suchas rings or the like, and grinding material into the inner space formedby the wall 2 and plate 4 and rotating the plate part 4 at a high speedthereby grinding the workpieces with the grinding material. Duringoperation, the grinding material reaches the region of the gap S. Due tothe elasticity of the elastic lining 8, the abrasive effect on it isrelatively small. The abrasive effect is larger on the ceramic ring, inparticular in the region of its inner lower edge 21.

[0016] It has turned out that the abrasive effect and therefore the wearof the ceramic ring is considerably smaller with the inventive designcompared to that of prior art.

List of Reference Numerals

[0017]1 Grinding machine

[0018]2 wall part

[0019]3 drive shaft

[0020]4 rotary plate part

[0021]6 stationary lower part

[0022]7 elastic lining

[0023]8 elastic lining

[0024]9 ceramic ring

[0025]11 inner wall

[0026]12 upper wall side

[0027]13 rear wall

[0028]14 nose-like projection

[0029]14 a nose

[0030]16 inclination

[0031]17 lower wall region

[0032]18 projection

[0033]19 upper side

[0034] A axis of rotation

[0035] S gap

I claim:
 1. A grinding machine comprising: a stationary wall member; aplate member disposed for rotation about an axis; a ceramic partintegral with one of said wall member and said plate member; and anelastic part integral with an other of said wall member and said platemember, wherein said ceramic part is disposed vertically above saidelastic part to define a gap between said ceramic part and said elasticpart.
 2. The grinding machine of claim 1, wherein said elastic part isintegral with a lining of said plate member.
 3. The grinding machine ofclaim 1, wherein said ceramic part is a ceramic ring disposed in a lowerregion of said wall member.
 4. The grinding machine of claim 1, whereinsaid elastic part has a flat surface.
 5. The grinding machine of claim1, wherein said axis of rotation is vertical.
 6. The grinding machine ofclaim 1, wherein said ceramic part has a downwardly facing nose-likeprojection.
 7. The grinding machine of claim 1, wherein an inner wall ofsaid plate member and an inner wall of said wall member taper from a toptowards a bottom above and below said gap in a substantially conicalmanner.
 8. The grinding machine of claim 7, wherein said taper definesan angle of inclination relative to said axis of rotation of between 30°and 45°.